Scanner technology is one of the most significant developments of the past few years in the field of image processing. Scanners allow an image to be entered in digitized form into a computer's data bank, where it can later be edited and manipulated as a bit-mapped graphic image.
For the purpose of this specification the term "hard copy" is meant to convey any sheet of paper or other material with text or graphic information thereon. This is the original from which one might wish to produce an electronic copy by a scanning operation.
The most common scanners in use today are flatbed and roller-fed scanners. In the first, a page to be scanned is laid on top of a glass cover and is in turn covered by another heavy opaque sheet to keep out light. In the second type, the roller-fed scanner, a sheet is inserted between rollers. This type is typically limited to single sheet scanning. FIG. 5 shows a prior art flatbed scanner 1 which accepts a hard copy 3 laid on platen 5 and electronically takes a picture of it, digitizes that picture, and enters it into the data bank of a connected computer (not shown). The scanner connects to the computer by means of cable 7 to the computer's serial port.
One of the difficulties of working with a flatbed or roller-fed scanner is that these devices are generally large and bulky and not easily ported from one location to another. They are relatively expensive and are composed of many fragile parts, such as a sensitive lens that needs to be handled gently to preserve alignment.
FIG. 6 shows a hand-held scanner 9, another type of scanner in popular use. This is a small hand-held device that is moved slowly across part of a scene or image, starting each pass across the page at a lower point than the last pass, making certain that the bottom of the last scan pass appears at the top of the present pass (or the reverse if a scan is begun at the bottom of an image). Several passes are typically required to input a full page, and there must be a means to deal with the overlap necessary to obtain a full image. Problems with hand-held scanners include bypassing areas due to untimely or incorrect movement and maintaining the proper dimensions of an image. Hand-held scanners, being small, have the additional problem of being easily misplaced under desktop clutter, and are also easily dropped and damaged.
Scanners, as charge-coupled devices, typically have little or no on-board memory, which adds to the expense of operation since all memory requirements must be met by the host computer. The connected computer must also manage the scanner's operation, and must therefore be compatible with that particular brand of scanner. The complexity of connecting a scanner to a computer can present problems, and alternative methods of entering an image into a computer data bank can include time-consuming drawing or re-typing, or the expense of digitizing equipment.
What is clearly needed is an apparatus and method in which scanning can take place simply, requiring no more than a computer, such as a notebook or lap-top unit, electronic circuitry included in that computer for scanning an image, and a means of utilizing the computer's display in the scanning operations, effectively making the computer also a scanner.